Adoptive immunotherapy with autologous tumor infiltrating lymphocytes (TIL) has been shown to mediate significant tumor regression in ˜50% of patients with refractory metastatic melanoma (Dudley et al., Science 298: 850-854 (2002) and Dudley et al., J. Clin. Oncol. 23: 2346-2357 (2005)). However, the isolation of TIL requires invasive surgery, which can lead to post-operative complications and delays in initiating adoptive immunotherapy with TIL.
The use of lymphocytes from peripheral blood (i.e., peripheral blood lymphocytes (PBL) or peripheral blood mononuclear cells (PBMCs)) in adoptive immunotherapy, in place of TIL, has been postulated as having several advantages. For example, procuring tumor reactive PBLs from a blood draw or leukapheresis avoids the need for invasive surgery. Also, the broad repertoire of PBL might allow for the isolation of unique populations of tumor-reactive lymphocytes that are not commonly found in TIL. Finally, the use of PBL might allow for the use of a generalized strategy to obtain tumor-reactive lymphocyte populations from patients, regardless of the diversity of the histology, thereby, expanding the therapeutic relevance of this approach.
A significant obstacle to the use of PBL in adoptive immunotherapy has been the lack of the availability of efficient in vitro methods to rapidly isolate and expand tumor reactive T cell clones from the peripheral repertoire. Many attractive tumor antigens are derived from normal self proteins, and conventional views of immunologic tolerance suggest that T cells reactive against these self antigens are rare in the natural peripheral repertoire and are predominantly of low functional avidity, incapable of recognizing tumor cells.
In view of the foregoing, there is a need for a rapid and efficient method of obtaining a population of antigen-specific T lymphocytes, especially rare antigen-specific T lymphocytes, from the peripheral blood of a host.